This invention relates to an improved process for producing toners and developers of specific, customer selectable colors. More particularly, this invention relates to a process whereby color pellets of the toners are blended prior to the grinding of the pellets and mixing of the ground toner powders into a final toner or developer composition. Such process is particularly useful in the production of toners and developers for use in single-pass electrostatographic imaging systems.
Conventional toners, resins and methods for producing such toners and resins are well known in the art.
Several methods of producing blended color toners and developers are also known in the art. For example, U.S. Pat. No. 4,312,932 discloses toners and developers wherein the developing composition comprises a single carrier and resin particles containing up to four pigments. The process involves incorporating multiple appropriate pigments into the resin, for example, by blending the pigments together in the molten resin during the processing and preparation of the resin, to yield a toner or developer with the desired specific color. As a further example, U.S. Pat. No. 4,395,471 describes a process whereby three separately prepared color toners are mixed in an appropriate ratio to yield a final toner composition of a desired specific color. In that process, previously-prepared yellow, cyan, and/or magenta toners are mixed together in their powdered or ground form and then combined with a single carrier to yield a developer with a specific customer selectable color. A similar process is also disclosed in U.S. Pat. No. 5,204,208, which describes forming a custom color toner by mixing together specified amounts of at least two encapsulated toners of different colors.
Conventional methods for producing color toners possess several disadvantages. These include difficulties in the handling and storage of the toner powders and the diseconomies of scale in producing small batches of specific customer selectable color toners. For example, if the color toner is produced by the method of incorporating the colorants directly into the resin, it is very uneconomical to produce small batches of such color toners. Further, where the color toner is produced by a method wherein the component toners and/or colorants are utilized in a powdered form, it is more difficult to handle and store the powdered compositions. Furthermore, it is sometimes difficult to ensure that blending of the powders results in a homogeneous toner composition, resulting in a toner with poor or inconsistent print qualities.